This document focuses mostly on the Ontology Middleware features. However it is just an extension of Sesame from aidminstrator b.v. and for many issues the Sesame documentation have to be consulted at http://sesame.aidministrator.nl/ Sesame and the Ontology Middleware are open source and available for download and contributions at http://sourceforge.net/projects/sesame/Abstract Ontology Middleware Module (OMM) is an extension of the Sesame RDF(S) (http://www.aidministrator.nl/) repository that supports tracking changes, meta-information, fine-grained access control, and multi-protocol client access (RMI, SOAP). This document presents the implementation of OMM after the analysis and design presented in [Kiryakov et al, 2002]. It provides short overview of the principle definition of the problems as they are approached in OMM and the Knowledge Control System, which is a substantial part of it. The most part of the document provides information for the installation, sample knowledge bases, test cases and scenarios, implementation details, reference guide for the API, and performance considerations. Acknowledgements Big part of the Ontology Middleware presented here was carried out in the course of the OnTo Knowledge project. Jeen Broekstra for the instant support and most especially for the timely implementation of the truth maintenance system of Sesame. Availability Most up to date version of the current document could always be found at